Development of Nervous System Flashcards
Describe the process of neuralation
1) notochord induction forming neural plate
2) neural plate deepens to form neural groove
3) groove folds together in midline and break free to form neural tube
4) neural tube goes to form brain and spinal cord
What does the centre hollow space of neural tube become?
the ventricular system
Neural tube is initially ________ thick with a ______ centre. There is a rostral to caudal gradient of formation, and ______ is older
one cell
hollow
rostral end
Describe the order of neural fold closure as they are independent events
closure goes in the order of
1) mid back
2) head to just above top of the neck
3) front of forehead
4) back of the head, between step 1 + 2
5) tail end
Failure of closing the tail end = ?
Is it common? what are the possible consequences?
spina bifida
yes, it is the most common defect of neural fold closure
get a blister of open neural tube + movement deficit in the lower limbs
What is the most severe form of neural fold defect?
anencephaly - still born baby lacking higher brain centre
What are the three initial swellings of neural tube in the rostral end? How many cell layers are in each swelling?
Prosencephalon, mesencephalon, rhombencephalon
1 cell thick still
What are the two distinct fissures during tube segmentation?
cephalic and cervical flexures
What does prosencephalon split into?
telencephalon and diencephalon
List the PNS neural crest derivatives
DRG, SNS/PNS/ENS ganglia, Schwann cells
How are optic vesicles formed? What do they become? What is the significance of it?
outpockets of diencephalon, and go on to become the retina. Retina injury has CNS pattern
What do neural crest cells give rise to apart from PNS structures?
melanocytes, muscle/cartilage bones of the face, dentine
T/F developing cells are very mobile
True, neural crest cells can migrate a fair distance
Enteric neural crest migration begins at the _______ all the way to _______ . it is the _______ network of migration. The same migrating pattern can be seen in ______ cells
oesophagus
anus
largest
cancer
What type of cell is the neuroepithelium of neural tube?
columnar
Describe the process of adding layers to generate cortex
proliferation of cells occur in the ventricular zone and daughter cells migrate to outer surface via radial glial cells.
The process is “inside-out” - adding cells on the inside, but cells migrate to the outside
What is a stem cell
cells that can self renew indefinitely and remain undifferentiated
Which genes can mutate and result in smooth, unfolded brain surface and mental retardation?
Reelin and DCX
What is the most common cause of male autism?
Fragile X syndrome, affecting the connectivity of brain
T/F neurons controlling distal muscles are more medial in the spinal cord
False, the organisation follows topographic organisation such that neurons for limbs are located laterally
T/F Motor neurons are ventral to sensory neurons
True, “dorsal” root ganglion houses sensory neuron cell bodies, and they are located dorsally
In spinal cord development, the notochord releases _______ to induces the formation of _________ , which will in turn use the same molecule to induce formation of _______ in the _______ horn
sonic hedgehog
floor plate
motor neurons
ventral
how do interneurons form?
motor neurons release motor-neuron factor to induce formation of interneurons
Describe the first step of axonal growth
when the embryo is still small, pioneer axons lay down the initial scaffold of axon tracts for later axons to navigate
What is a growth cone
the tip of axon and the site of axon extension.
Cell body just adds material for axons to extend
How do axons know where to go?
they follow gradients of chemical in the embryo, which can either attract or repel them
What is the critical period
refinement of the imperfect, infant nervous system, leading to permanent changes that establish mature functional nervous system.
Can occur postnatally
T/F visual input from left and right eyes are segregated
True, and this can be seen in visual cortex where there are alternating bands
What happens if we sew shut a cat’s eye during the critical period?
the sewed eye is likely to become permanently blind, and it’s not because the retina is not working, but because the visual cortex is not responding
What is the principle of plasticity in critical period
use it or lose it, and it’s the relative activity that’s important
repetitive stimulus is potentiated
unused information is depressed
